Early ornithologists often mistook the calling of the Mockingbird as the rare Rufous Sided Towhee

A. calling of the Mockingbird as the rare Rufous Sided Towhee
B. call of the Mockingbird for that of the rare Rufous Sided Towhee
C. call of the Mockingbird as the rare Rufous Sided Towhee
D. calling of the Mockingbird for that of the rare Rufous Sided Towhee
E. Mockingbird calling for the rare Rufous Sided Towhee

OA: A

Why is call preferred over calling?